Experimental Study on the Influence of Staged Oxygen Consumption on the Oxidation Characteristics of Coal Spontaneous Combustion

The oxidation characteristic parameters of residual coal in working face change with the advance of coal seam. To explore the influence of dynamic oxygen-consuming environments, we examined the influence of reducing the oxygen concentration on the formation characteristics and characteristic parameters of coal oxidation products, conducted with temperature-programmed experiments under staged oxygen consumption. The correlation between the characteristic oxidation parameters was determined, and the critical oxygen concentration that determined the gas yield was obtained. The results show that after staged oxygen-consumption, the oxidation of coal is stronger than that under constant low oxygen, the oxidation products are greatly affected, and the influence of pyrolysis gas is small. The oxidation characteristic parameters such as gas product volume fraction, production rate, and heat release intensity are positively correlated with the oxygen-consumed temperature. We found that the oxidation reaction heat of coal is 180~330 kJ·mol−1, and the maximum and minimum exothermic intensities are significantly linearly correlated with the oxygen consumption rate. Finally, the critical oxygen concentrations for gas production rate under oxygen-consumed conditions were 17, 9, and 5%. These results have practical significance for strengthening the prevention and control of spontaneous combustion disasters in goafs.